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Chapter 21: Histamine, Bradykinin, and Their Antagonists

This antihistamine has antiemetic effects useful in treating vertigo or postoperative emesis.

a. Cetirizine

b. Loratadine

c. Fexofenadine

d. Promethazine

e. None of the above

Answer is d. The antiemetic effects of some first-generation H1 antagonists (eg, dimenhydrinate, cyclizine, meclizine, and promethazine) can be beneficial in treating vertigo or postoperative emesis. Dimenhydrinate and meclizine often are of benefit in vestibular disturbances such as Ménière disease and in other types of true vertigo. Only promethazine is useful in treating the nausea and vomiting subsequent to chemotherapy or radiation therapy for malignancies; however, other, more effective antiemetic drugs (eg, 5-HT3 antagonists) are available (see Chapter 33).

This antihistamine is approved for use in children.

a. Cetirizine

b. Meclizine

c. Promethazine

d. Diphenhydramine

e. None of the above

Answer is a. The second-generation H1 antagonists—loratadine, desloratadine, fexofenadine, cetirizine, levocetirizine, and azelastine (intranasal)—have been approved by the FDA for use in children and are available in appropriate lower-dose formulations (eg, chewable or rapidly dissolving tablets, syrup). First-generation antihistamines are not recommended for use in children because their sedative effects can impair learning and school performance.

The H1 antihistamines are highly effective in treating this histamine-mediated process in humans.

a. Gastric secretions

b. Anaphylactic bronchospasm

c. Allergic urticaria

d. Bronchial asthma

e. Severe angioedema

Answer is c. H1 antagonists are most useful in acute types of allergy that present with symptoms of rhinitis, urticaria, and conjunctivitis. Their effect is confined to the suppression of symptoms attributable to the histamine released by the antigen-antibody reaction. In bronchial asthma, histamine antagonists have limited efficacy and are not used as sole therapy. In the treatment of systemic anaphylaxis, where autacoids other than histamine are important, the mainstay of therapy is epinephrine; histamine antagonists have only a subordinate and adjuvant role. The same is true for severe angioedema, in which laryngeal swelling constitutes a threat to life.

The antihistamine of choice in treating seasonal allergy symptoms in a pregnant woman is

a. cetirizine.


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